Wheels Manufacturing Sealed Bearings SB-6803-17.0/26.0/5.0 (Bag of 2) High chromium steel bearing races. High quality rubber seals that won't interfere with the balls themselves. The seals simply seal out contamination without increasing any rolling resistance High quality lithium grease. These bearings are acceptable replacements for any OEM bearing, already on your bike, they are economical and long lasting